Synthesis and properties of LiM II PO 4 (M II  = Mg, Mn 0.5 Mg 0.5 , Co 0.5 Mg 0.5 ) affected by isodivalent doping and Li-sources

Solid State Reaction Mechanisms of the LiMnPO4 Formation Using Special Function and Thermodynamic Studies

“…Isoconversional procedure, − the thermal decomposition kinetic investigation of the single crystalline compounds, is a solid-state reaction of the type: A (solid) → B (solid) + C (gas) − as well as the solid-state reaction of two or more solids can be described as the type of ∑ A i (solid) → ∑ B j (solid) + ∑ C k (gas). ,, The nonisothermal (isoconversional) kinetic model is a model-free method, which involves measuring temperatures ( T ) corresponding to the fixed value of extent of conversion (α) at different heating rates (β, β = (d T /d t )/°C min –1 , t is time/min). The α-values from thermogravimetric analysis may be defined as the ratio of actual mass loss to the total mass loss corresponding to the investigated process: where m t is the mass of the sample at time t , and m 0 and m f are the masses of the sample at beginning and end of the mass loss in the TG curve reaction results, respectively.…”

“…Olivine structure phosphates, LiM II PO 4 (M II = Fe, Mn, Co, Ni), have attracted considerable attention because of their being nontoxic, environmentally friendly, and having excellent thermal stability. − The first olivine structure LiFePO 4 was reported in 1997 to be used as a cathode material for Li-ion battery by Padhi et al It has been substantially investigated and successfully commercialized due to its excellent rate capacity, stable cycling performance, and low cost in that period of time. − After that, the isostructural LiMnPO 4 was considered as the next promising cathode material because of its higher operating voltage (4.1 V) and theoretical capacity (170 mAh g –1 ) than those of LiFePO 4 . , Besides, the higher operating voltage is also well within the typical electrolyte stability window . In the previous works, , the lithium single- and binary-metals of LiM II PO 4 (M II = Mn, Mg, Mn 0.5 Mg 0.5 , and Co 0.5 Mg 0.5 ) were synthesized via their hydrate precursors (NH 4 M II PO 4 ·H 2 O) and compared between two different Li sources of LiOH·H 2 O and Li 2 CO 3 and found that Li 2 CO 3 exhibited smaller particle size. In addition, the nonisothermal kinetic triplets including activation energy E α , pre-exponential factor A , and the reaction mechanism functions f (α) or g (α) from the formation processes of LiMnPO 4 from NH 4 MnPO 4 ·H 2 O precursor were studied and reported using Ozawa–Flynn–Wall (OFW), Kissinger–Akahira–Sunose (KAS), Coat–Redfern, and multiple heating scan rates methods. , The related thermodynamic functions (Δ H ‡, Δ S ‡, and Δ G ‡) of the transition state complexes are also evaluated and reported.…”

“…In the previous works, , the lithium single- and binary-metals of LiM II PO 4 (M II = Mn, Mg, Mn 0.5 Mg 0.5 , and Co 0.5 Mg 0.5 ) were synthesized via their hydrate precursors (NH 4 M II PO 4 ·H 2 O) and compared between two different Li sources of LiOH·H 2 O and Li 2 CO 3 and found that Li 2 CO 3 exhibited smaller particle size. In addition, the nonisothermal kinetic triplets including activation energy E α , pre-exponential factor A , and the reaction mechanism functions f (α) or g (α) from the formation processes of LiMnPO 4 from NH 4 MnPO 4 ·H 2 O precursor were studied and reported using Ozawa–Flynn–Wall (OFW), Kissinger–Akahira–Sunose (KAS), Coat–Redfern, and multiple heating scan rates methods. , The related thermodynamic functions (Δ H ‡, Δ S ‡, and Δ G ‡) of the transition state complexes are also evaluated and reported. Our recent work reported the isoconversional kinetics, reaction model, and thermodynamic studies of NH 4 Co 0.8 Zn 0.1 Mn 0.1 PO 4 ·H 2 O using the iterative method of KAS equation to determine the exact E α values.…”